The present invention relates to extensively applicable photo machining apparatus and photo machining methods for machining inorganic transparent materials nanometrically (with a precision on the order of up to several nanometers). They are used, for example, in the field related to optically functional parts such as photonic crystals and optical waveguides, and microchip chemistry such as DNA analyses and blood tests.
Inorganic transparent materials are highly valued for use in the fields of optical materials, such as photonic crystals and optical waveguides, and nanometric chemical analyses and chemical reactions in medicine and biotechnology, and accordingly, highly precise and less costly techniques for the fabrication and modification of inorganic transparent materials are in demand.
A technique called laser ablation, in which a material is strongly irradiated with a laser beam and the irradiated surface is fabricated by ablation, has already been used practically in metal fabrication using carbon dioxide gas laser. The most advanced photo machining technology in terms of nanometric precision is represented by photo lithography, in which the machining precision is limited by the wavelength of laser light used for machining and is on the order of about 100 nm at the best. In order to perform finer machining, use of the light with a wavelength of 10 nm, namely soft X-ray, is necessary, which increases the machining cost.
Further, it is difficult to fabricate inorganic transparent materials by conventional photo machining techniques because the inorganic transparent materials are transparent and do not absorb laser light.
Conventional techniques already known as photo machining techniques for inorganic transparent materials are described as follows.
(1) A technique to perform laser machining by immersing a material to be machined in a photosensitizing medium solution has been reported but the machining precision has not reached on the order of the wavelength.
(2) It is reported that when laser plasma produced by laser ablation is brought into contact with the surface of a material to be machined and then this surface is irradiated with laser light for machining, the material to be machined is ablated by the plasma which absorbs its energy. However, also in this technique, the machining precision has not reached on the order of the wavelength.
(3) It is reported that when silicon dioxide is irradiated with an F2 laser beam, absorption is generated in the state originated from non-crystality and modification can be performed by simultaneous irradiation of a strong KrF (krypton fluoride) laser beam in this state. This technique cannot be extensively used because of a prerequisite that the state of the first laser beam absorption is present in advance.
(4) Absorption can occur even with a transparent material by irradiating a material to be machined with a femtosecond laser beam for multi-photon absorption, in which multiple photons are simultaneously absorbed, and thereby fabrication such as ablation and modification can be performed; however, the machining precision is on the order of the wavelength.
(5) It is reported that interference generated between two beams of femtosecond laser light on the surface of a material to be machined allows ablation with the interference pattern of several nanometers. However, patterns that can be ablated are limited.
The present invention is to provide extensively applicable fabrication techniques to machine inorganic transparent materials at a precision on the order of up to 10 nm without problems associated with conventional fabrication techniques.
In order to solve the abovementioned problems, the present invention provides a photo machining apparatus comprising a patterning light source to emit ultraviolet light or soft X-ray, a patterning irradiation means, and a machining laser beam source, characterized in that said patterning irradiation means is to irradiate an inorganic transparent material with said patterning light in a predetermined pattern matching to a shape to be machined and then generate new light absorption in a part of said inorganic transparent material irradiated with said patterning light in said predetermined pattern, and said machining laser beam source is to irradiate said inorganic transparent material with a machining laser beam to allow said machining laser beam to be absorbed only at the part of said inorganic transparent material where said absorption is generated, thereby machining said inorganic transparent material.
The abovementioned patterning light source is characterized in that it emits a light with a wavelength from a ultraviolet light to soft X-ray, which has a photon energy higher than the bandgap of said inorganic transparent material, a photon energy corresponding to excitation to the tail state, or a photon energy corresponding to the energy for direct excitation of the excitons.
The abovementioned patterning irradiation means is characterized in that it is a means to perform patterning by focusing beams on the inorganic transparent material using a beam-focusing optical system and then scanning a stage which supports the inorganic transparent material.
The abovementioned patterning irradiation means is characterized in that it is a means to scan and irradiate said inorganic transparent material with a patterning light via a scanning mirror in accordance with said pattern.
The abovementioned patterning irradiation means is characterized in that it is a means to transcribe said pattern onto said inorganic transparent material using an imaging optical system.
The abovementioned patterning irradiation means is characterized in that it is a means to arrange a contact mask on the surface of an inorganic transparent material and irradiate said inorganic transparent material with a patterning light through the slit of the contact mask.
The abovementioned patterning light source is characterized in that it is a debris-free laser plasma soft X-ray using gas as a target.
In order to solve the abovementioned problems, the present invention provides a method for photo machining characterized in that an inorganic transparent material is irradiated with a patterning light in a predetermined pattern matching to a shape to be machined to generate new light absorption and the inorganic transparent material is simultaneously irradiated with a machining laser beam so that machining is performed by allowing said machining laser beam to be absorbed only in a part of said inorganic transparent material where the absorption is generated in said predetermined pattern.
According to the present invention comprising the abovementioned structure, the absorption in the ultraviolet or visible region can be generated by transiently patterning an inorganic transparent material with soft X-ray having a high spatial resolution of up to about 10 nm, and then only the patterned part of the inorganic transparent material can be machined by further irradiation of a machining laser beam having a wavelength matching to said absorption that can maintain a high energy density, although it is difficult to maintain the high energy density in terms of cost and technology.